# Introduction
`QRY` is a command introduced with [MSNP6](../versions/msnp6.md).

It is a Notification Server command, WITH a request payload but without a response payload.

Responds to a challenge request ([CHL](chl.md) command).

# Client/Request
```
QRY TrID public-key length
payload
```

Where `public-key` is your client's Public Key.
For a list of valid Public Keys, read the [Challenge Key Pairs](../files/challenge_keypairs.md) article.

Where `length` is the size (in bytes) of the `payload`.

Where `payload` is the challenge response.

## Challenge responses
Calculating the challenge response depends on the version of the protocol you are using.

For a list of valid Private Keys, read the [Challenge Key Pairs](../files/challenge_keypairs.md) article.

### Basic responses
*Only in [MSNP6](../versions/msnp10.md) to [MSNP10](../versions/msnp10.md).*

Simply MD5 hash the challenge and your client's Private Key concatenated together as a string.

The output should be 32 bytes and lowercase hexadecimal.

### Advanced responses
*Since [MSNP11](../versions/msnp11.md).*

Since this is more advanced of an algorithm,
it will be avaliable as annotated source code in the Miscellaneous Files sectiom.

TODO: Write said annotated source code.

The output should be 32 bytes and lowercase hexadecimal.

# Server/Response
`QRY TrID`

# Examples

## Successful response
```
S: CHL 12345678901234567890
C: QRY 1 msmsgs@msnmsgr.com 32
8ba1bb9d6dbf624fee31a2053af5fdd0
S: QRY 1
```

## Failed challenge
*NOTE: This happens as-is in [MSNP11](../versions/msnp11.md),
since it isn't using the new method.*
```
S: CHL 12345678901234567890
C: QRY 2 msmsgs@msnmsgr.com 32
8ba1bb9d6dbf624fee31a2053af5fdd0
S: 540 2
```

Server disconnects client.

# Known changes
* [MSNP11](../versions/msnp11.md): Changed challenge response generation algorithm drastically.